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François Andrieu

ANDRIEU François, PhD

Géosciences Paris Sud (GEOPS)

Bâtiment 504, Rue du Belvédère

Campus Universitaire d’Orsay

91405 Orsay Cedex, FRANCE

mail : francois.andrieu@u-psud.fr


Research interests

- Surface spectroscopy
- Radiative transfer in ices
- Inversion methods for spatial remote sensing data
- CO2 cycle on Mars
- Seasonal processes on Mars

Keywords

Mars, Radiative Transfer, Remote Sensing, CO2 ice, Water ice, Massive Inversion, Spectro-imaging


Ph.D thesis

Title: Caractérisation des surfaces glacées de Mars par imagerie hyperspectrale : inversion du transfert radiatif.

Defense on friday, december 11, 2015.

Committee members:

  • M. Emmanuel Lellouch, Astronomer, Observatoire de Paris LESIA/CNRS
  • Mme Cécile Ferrari, Professor, Université Paris Diderot-Paris 7
  • M. Yves Langevin, Research director, CNRS
  • M. Xavier Briottet, Professor, ONERA-DOTA/ISAE
  • M. Éric Chassefière, Research director, CNRS
  • M. Karri Muinonen, Professor, University of Helsinky
  • M. Frédéric Schmidt, Assistant professor, Université Paris-Sud, Ph.D supervisor
  • M. Bernard Schmitt, Research director, CNRS, Guest
  • M. Sylvain Douté, Researcher, CNRS, Guest

Abstract: Mars has a complex climate characterized by carbon dioxide and water cycles and dust transport at all scales. These cycles are mainly controlled by the seasonal condensation of CO2 and water ice deposits at high latitudes during the polar night and their sublimation during the local spring. There are many interactions between the CO2, water and dust cycles on Mars and they influence each other. An active seasonal process illustrates particularly well these links: the cryoventing, cold CO2 gas jets triggered by seasonal sublimation of CO2 deposits, which can hurl dust from the regolith in suspension into the atmosphere durably, and whose activity seems to be modulated by the exchange of water at the surface. The purpose of this thesis is to allow the use of the available hyperspectral imaging data to their full potential, to bring new constraints on seasonal exchanges between surface and atmosphere and the interactions between the different cycles (CO2, water , dust), focusing on cold gas jets. To achieve this, a semi-analytical radiative transfer model for compact ices and an effective inversion method were developed and validated. The radiative transfer model describes the quantitative interaction of light with a slab, using the following parameters: thickness of the layer, volume proportions and grain-sizes of impurities, surface roughness. It is based on several key assumptions: geometrical optics, piecewise-continuous media quasi-spherical inclusions. The two-stream approximation is used for the radiative transfer inside the layer, but the surface specular reflectance is estimated taking into account the variability of the facets orientations from the surface roughness. This model was validated both numerically and on laboratory data. The inversion method consists in exploring synthetic databases generated by the radiative transfer model and determining the most likely sets of parameters to reproduce a given measure. The inversion is based on the Bayesian formalism: the manipulated variables are described by probability density functions. This allows taking into account realistic uncertainties on the data and enables to calculate a posteriori uncertainties on the result of the inversion. A focused study was conducted on a area of particular interest, to test and prove the applicability of this approach to the massive inversion of spectro-imaging data. We determined the surface properties of the Richardson Crater dune field (72°S, 180°W), chosen because it shows strong interactions between the water and CO2 cycles, a major seasonal cryoventing activity, but also a large amount of data available and a high quality temporal monitoring. The monitoring of surface characteristics on this site shows a decrease in the thickness of the ice during the spring consistently with climate models simulations. We were able to estimate and monitor the content of water and dust in order to discuss the formation scenario of cold jets. We proposed a new mechanism of small water ice grain suspension.


Current projects

Radiative transfer inversion of spectro-imaging data: Martian seasonal CO2 deposits

The goal is to characterize the seasonal evolution and spatial variations of the ice covered surfaces on Mars, to better constrain the exchanges between the surface and the atmosphere in connection with the observed active seasonal processes.

Experimental modeling modeling of active Martian surface processes

We are currently building an experimental platform able to condensate and sublimate CO2 ice in Martian conditions, to better understand the dynamic mechanisms of active seasonal surface processes on Mars.


Teaching and Administration experience

2013-: Ph.D. students representative at the OSUPS council (Paris-Sud Science of the Universe Observatory).

2013-: Teaching assistant in physics. I am giving practical lessons at IUT d’Orsay, in the physical measurements department. I teach in materials structure (X ray emission, absorption and diffraction, crystallography) and in materials properties (stress, strain, stiffness, Young’s modulus...)

2012-2013: Voluntary tutoring in a disadvantaged area (ZEP/REP : Educational Priority Area) for eighth graders.


Education

2012-: Ph.D. student in Planetary Science at GEOPS (Geoscience Paris-Sud) on the subject: Characterization of ice covered terrains on Mars using spectra-imaging data: a radiative transfer inversion.

2012: M.S. Ocean, Atmosphere, Climate ans Spatial Observations, with a speciality in physical methods for remote sensing, with honors (UPMC, Paris VI)

2010: B.S. Physics and Applications, with honors (UPMC, Paris VI)

2009-2011: PhyTEM Course, Physics, Theory, Experience, Model (UPMC-ENS Cachan, last year of Bachelor’s + first year of Master’s)

2009-2013: Student "normalien" at École Normale Supérieure of Cachan (physics department)


Publications

Refereed journal articles:

- Andrieu, F., Douté, S., Schmidt, F., Schmitt, B. (2015). Radiative transfer model for contaminated rough slabs, Applied Optics, OSA, 54, 9228-9241.

- Andrieu, F., Schmidt, F., Schmitt, B., Douté, S., Brissaud, O. (2015). Radiative transfer model for contaminated rough slabs: experimental validations, The Cryosphere Discussions, 9, 5137-5169, in revisions.

Communications in international conferences:

- Andrieu, F. ; Nachon, M. ; Schmidt, F. ; Gargani, J. & Douté, S. (2012) CO2 ice state at the Martien dark spots, European Planetary Science Congress 2012, 1, 892 oral

- Andrieu, F. ; Schmidt, F. & Douté, S. (2013) Radiative transfer inversion for hyperspectral data set on Mars. European Planetary Science Congress 2013, held 8-13 September in London, UK., 8, 147 oral

- Andrieu, F. ; Schmidt, F. & Douté, S. (2013) CO2 ice state during active Dark Spot, European Planetary Science Congress 2013, held 8-13 September in London, UK., 8, 149 oral

- Andrieu, F. ; Schmidt, F. & Douté, S. (2014) CO2 Ice Composition and Evolution on Mars : A Radiative Transfer Inversion, Lunar and Planetary Science Conference, The Woodlands, Texas, 45, 1148 oral

- Andrieu, F. ; Schmidt, F. & Douté, S. (2014) Spectroscopic evidence for translucent CO2 ice in Richardson crater, European Planetary Science Congress 2014, 9, 537 oral

- Andrieu, F. ; Schmidt, F. ; Doute, S. & Schmitt, B. (2015) CO2 Ice state on Mars, EGU General Assembly, 2015, 17, 10188 oral

- Andrieu, F. ; Schmidt, F. ; Doute, S., Schmitt, B. & Brissaud, O. (2015) Radiative transfer model for Solar System ices, European Planetary Science Congress 2014, Nantes, 10, 91 oral

Communications in international workshops:

- Andrieu, F. ; Schmidt, F. ; Chassefière, E. (2013) Spectrocopic study of Martian ices, OMEGA meeting, Venice, june 10-12 2013 oral

- Andrieu, F. (2013) Active CO2 jets and spiders on Mars, Workshop Mars IV, Les Houches, France, 20-25 October 2013 poster

- Andrieu, F. ; Schmidt, F. ; Doute, S., (2013) CO2 ice characterization on Mars : a radiative transfer inversion, Workshop I2-MARS, Grenoble oral

- Andrieu, F. ; Douté, S. ; Schmidt, F. (2014) Radiative transfer model for contaminated slabs, Planetary cryosphere workshop, Nantes oral

Communications in national conferences:

- Andrieu, F. ; Chassefière, E. & Schmidt, F. Étude spectroscopique d’écoulements martiens. Atelier du pôle système (2013) solaire de l’IPSL, 17-18 avril 2013 oral

- Andrieu, F. ; Schmidt, F. ; Doute, S. (2014) Caractérisation de la glace de CO2 sur Mars par télédétection hyperspectrale, colloque SFPT-GH, Porquerolles, mai 2014 oral

- Andrieu, F. ; Schmidt, F. ; Doute, S. (2014) Caractérisation de la glace de CO2 sur Mars par télédétection hyperspectrale, colloque du PNP, Paris, octobre 2014 poster

- Andrieu, F. ; Schmidt, F. ; Doute, S., Schmitt, B. (2015) Radiative transfer model for Solar System ices, Rencontres des jeunes physiciens, Paris poster

- Andrieu, F.; Schmidt, F., Inversion bayesienne avec des tables de données (2015), colloque Image’In, Orsay, novembre 2015 oral

- Andrieu, F.; Doute, S.; Schmidt, F.; Simulation du transfert radiatif pour des couches compactes (2015), colloque Image’In, Orsay, novembre 2015 oral





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